Method and means for producing motor armatures



Aug. 29, 1933. E. P. LARSH 1,925,052

'METHOD AND MEANS FOR PRODUCING MOTOR RMATURES Filed NOV. 21, 1929 2 Sheets-Sheet 2 Patented Aug. 29, 193.3Y

' UNITED STATES PATENT OFFICE "METHOD AND MEANS FOR PRODUCING MOTOR ARMATURES Application November 21, 1929 Serial No. 408,844

is claims. (ci. .2a-155.53)

This invention relates to asynchronous or induction electric motors and more particularly to the construction and method of manufacture of rotors of the squirrel-cage type therefor.

A squirrel-cage rotor, as distinguished from a wire wound rotor, consists of heavy bars of low resistance metal embedded in semi-closed slots in the periphery of a laminated iron core, the bars being short circuited at both ends by being connected to heavy terminal rings of similar low resistanceI material. To afford more uniform torque in starting and reduce the humming noise while running, such bars are skewed or inclined to the axis of the rotor.

Inasmuch as the currents circulated in the rotor are induced by the action of the magnetic field set up in the stator of the motor and are not produced directly by the power supply, the voltage generated in such squirrel-cage winding is low and no insulation is required upon the bars.

While the idea of integrally casting the terminal conductor rings and connecting bars of the rotor is not new, the present invention pertains more especially to a new method of effecting such casting of the terminal rings and bars by providing spaced permanent mold heads in which the ends of the laminated core assembly are engageable, and in which are positioned sand cores about which the rings are molded, the laminated core being exposed between the mold heads and peripherally vented to facilitate the escape of air and gasses during the casting operation.

In preparation for such casting operation, the laminas of the iron core are punched or perforated with openings which approach quite closely but do not quite intersect the margin of the laminas. These lamina are assembled with their perforations or holes in registry or in slightly offset or overlapping relation as may be necessary to accommodate the askew position of the bars, thus .forming continuous passages through the laminated core assembly. Interposed between such laminas, are other lamina wherein the opening or perforation intersects the margin thereof. Such latter style of laminas may be interspersed either in groups or in separated relation, and afford small vent openings from the passages within the core through the periphery thereof for the escape of air and gasses during the casting operation. The vented periphery of the laminated core being exposed between the mold heads, permits free escape of the vented gasses.

The object of the invention is to simplify the structure as Well as the means and method of manufacturing of squirrel-cage type rotors,

whereby they will not only be cheapened in construction, but will be more efficient in operation, of increased durability, of permanent form and assembly, and unlikely to get out of order.

A further object of the invention is to provide improved means for venting the laminated iron core preparatory to casting the rotor bars therethrough.

A further object of the invention is to provide improved form of permanent mold for the inte- 6 gral casting of terminal rings and connecting rotor bars wherein the vented periphery of the core will be exposed for free escape of gasses.

A further object of the invention is to provide molding means employing a sand core in combination with permanent molding heads.

A further object of the invention is to materially reduce the cost of manufacture and to facilitate the assembly of such motor rotors. r

A further object of the invention is to provide 7') a permanent assembly.

With the above primary and other incidental objects in View, as will more fully appear in the specification, the invention consists of the features of construction, the parts and combinations 0 thereof and the mode of operation or their equivalents, as hereinafter described and set forth in the claims.

Referring to the accompanying drawings wherein is shown the preferred but obviously not necessarily the only form of embodiment of the invention, Fig. l is a perspective view of the assembled sectional mold into which the laminated core is inserted for the casting of the terminal conductor rings and interconnecting bar.

Fig. 2 is a transverse sectional View of the mold heads and a rotor therein showing the relation of the sand core, the terminal rings and connecting bar. 9

Fig. 3 is a side elevation of the laminated core assembly preparatory to insertion in the mold.

Fig. is a side elevation of the completed rotor.

Figs. 5 and 6 are detail views of portions of the lamina or perforated plates which comprise the core; the plate illustrated in Fig. 6 having been shaved or reduced marginally whereby the slots or perforations intersect the margin of the plate or lamina to afford vent openings, whereas the slots or perforations of the plate illustrated in 1 Fig. 5 do not intersect the margin of the lamina, and when assembled aord a laterally closed passage.

Like parts are indicated by similar characters of reference throughout the several views.

Referring to the accompanying drawings, 1 is which are interconnected with each other by f integral bars 5 extending through the passages in the core assembly afforded by the slots or perfoi'ations 3. While copper has heretofore been commonly used for terminal rings and bars, in the present instance the rings 4 and bars 5 are preferably cast in situ'of aluminum.

Preparatory to integrally casting the rotor bars and terminal rings in permanent assembly with the core, the plates or lamin 2 of the core are provided with slots 3 which approach quite closely to the margin but do not intersect the marginal contour of the plates. When these plates are assembled, the passages formed by the registering perforations will be closed at the periphery of the rotor and open only at their ends for admission of molten metal. Interposed between such perforated or slotted plates 2 are a few additional plates 2a having similar perforations or slots 3a which, however, are extended to intersect the margins of the plates or lamin 2a. In practice the lamina: or plates are all formed identical as shown in Fig. 5 and then a limited number of plates are shaved or marginally reduced to slightly less diameter so that the marginal contour intersects the perforations or slots as shown in Fig. 6. These special plates 2a`, wherein the slot or perforation intersects the marginal line of the plate interposed between the plates or laminas 2 in which the perforations do not intersect the margins, may be disposed in small groups or may be distributed at spaced intervals throughout the assembly of plates 2. The openings afforded by the intersection of the margins `by the slots or perforations 3a afford small vent openings 6 communicating with the passages through the core assembly and which serve asvent holes for the escape of air and gasses from the passages during the casting operation.

The core assembly is then placed in a mold adapted to receive molten metal in which the end rings 4 are formed. This mold may be an ordinary sand mold, but is preferably a permanent mold of special design such as is illustrated in Fig. 1.

The mold illustrated in Fig. 1 comprises two molding heads 7-7 fixedly' interconnected in spaced relation with each other by tie rods or bolts 8. The mold heads 'I are formed in halves which are hinged at 9 upon a trunnion shaft 10 mounted in a suitable base 1l. The two halves of the molding head are normally held together by a detachable connection or latch 12. Each molding head is provided with a sprue or ingate 13 through which the molten metal is poured. The core assembly 1 is positioned intermediate the molding head 'l with its opposite ends extending within such molding heads and its medial peripheral portion containing the vent holes 6 exposed. Sand cores 14 are positioned in each of the molding heads 7 adjacent the ends of the core assembly affording thereabout annular chambers for the flow of the molten metal. The

metal deposited therein fills such annular spaces n and flows through the longitudinal passages formed by the registering perforations or slots 3 and 3a in the lamin, thus .forming bars 5 integral with the end rings 4. By thus molding the cage in situ, a permanent unitary structure is formed. The continuity of the bars and end rings increases the conductivity and obviates any resistance incident to mechanical joining of the rings and bars as in .the usual construction. Aluminum has been found to be highly desirable for this purpose, for it not only gives high electrical efficiency but also minimizes the weight of the rotor. The use of the sand cores 14 enables compensation for shrinkage of the rings within the mold and permits the finished casting to be readily removed from the permanent mold heads 7.

After removal of the rotor from the mold, the peripheral surface is reduced by turning in a lathe or by grinding or otherwise until the perforations or slots 3 of the plates 2, now filled with solid metal forming the bars 5, are intersected. This opens the slots or interrupts the surface of the rotor, exposing narrow portions of the cast bars therethrough as indicated at 15 in Fig. 4.

The vent holes 6 also facilitate inspection by enabling the workman to definitely ascertain that the metal to form the bars has completely filled the passages. If a perfect cast has been made, the cast metal will be visible at each vent hole 6 filling the holes and showing white. If the metal has failed to flow properly and has not formed perfect bars, the vent holes will appear black and empty.

'I'he sand core 14 affords a yielding or contractible body which will compensate for the shrinkage of the cast metal when cooling. Other forms of yielding or spring cores may be employed in lieu of the sand core. It has been found however that the sand core affords the most convenient and economical production.

In the present case the terminal rings and connecting bars are cast entirely without pressure. It is recognized that pressure casting and die casting processes have heretofore been employed for similar purpose. To temporarily hold the laminae in assembled relation until the casting operation is completed they are assembled upon a sleeve 15 through which is extended a 120 rod or bolt having at its ends clamp nuts 16 bearing upon clamp collars 17 surrounding the ends of the mounting sleeve 15 and bearing against the terminal lamin of the assembly.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable but which obviously is susceptible of modiflcation in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to complywlth the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific details shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into effect 'and the invention is, therefore, claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. The herein described method of producing squirrel-cage rotors for electric motors, including providing an assembly of perforated lamine arranged with their perforations disposed to afford continuous passages through the assembly,

the perforations of the greater number of such laminas being spaced from the peripheries thereof, the perforations of a lesser number of lamina: interposed between other lamin intersecting the peripheries thereof, inserting said assembly in a mold, positioning sand cores at the ends of the assembly, casting metallic end rings about the sand cores, and integral bars connecting the end rings through the passages and subsequently reducing the periphery of the assembly until the peripheries of all the laminations intersect the perforations thereof and expose the case bars therein.

2. The herein described method of producing squirrel-cage rotors for electric motors including punching in a series of lamin pluralities of holes which do not intersect the margins of the laminae and punching in a lesser number of lamina: plu- .ralities of holes which intersect the margins of such lamin, assembling the laminae into a rotor body with their holes disposed to aiTord continuous passages therethrough and with those lamina4 having holes intersecting their margins interposed between those, the holes of Whichdo not intersect their margins, inserting the assembled body within a mold, and casting molten metal conductor rings at the ends of the assembly and integral bars connecting said rings through the passages, the interposed laminae wherein the holes intersect the margins aiording vent holes for the escape of air and gases from the passages, and subsequently peripherally reducing the assembled body until the holes of all the laminze intersect their margins and expose the cast bars extending therethrough.

3. The herein described method of producing squirrel-cage rotors for electric motors including providing in a series of laminae pluralities of slots which do not intersect the margin of the lamin and providing in other laminas slots intersecting the margins of such laminas, assembling the lamina: into a rotor body with their slots disposed to aord continuous passages through the rotor body with those laminas of the latter style interposed between those of the rst style, casting integral end rings and connecting bars extending through said passages and subsequently reducing the periphery of the rotor body until the periphery intersects the slots of all of the laminae.

4. The herein described methodof producing squirrel-cage rotors for electric motors, including providing an assembly lof lamina having spaced passages therethrough, the periphery of the assembly being continuous, providing vent holes through the periphery of the assembly into said passages, integrally casting end rings at the extremities of the assembly and bars connecting the rings through said passages, and subsequently reducing the periphery oi the assembly until the cast bars are exposed therethrough.

5. A squirrel-cage rotor assembly including a plurality of lamin having holes which do not intersect the margins of the lamin, and other lamin interposed therebetween having holes intersecting their margins, said laminas being arranged wi'th their holes affording continuous passages, the intersection of the holes with the inargins affording vent holes communicating with said passages.

6. Ay squirrel-cage rotor assembly including a plurality of perforated lamin assembled with their holes relatively disposed in non-intersecting relation with the peripheries of the laminae to afford continuous passages through the assembly, said assembly having spaced vent openings from said passages to the periphery of the assembly.

7. The combination with an assembly of perforated laminae, the perforations of which are relatively disposed to aiTord continuous passages through the assembly, of a pair of mold heads between which the assembly is supported with its periphery exposed to atmosphere and having therein spaced vent openings communicating with the passages, sand cores centrally disposed Within said mold heads, said heads being adapted to receive molten metal which will be cast into rings surrounding the sand cores at the ends of the assembly and will extend through the passages to form integral bars connecting the end rings.

8. The combination with an assembly of perforated laminas, the perforations of which are relatively disposed in non-intersecting relation with the peripheries of the lamina: to aiord continuous passages through the assembly and having spaced vent openings in the periphery of the assembly communicating with said passages, of a pair of permanent molding heads arranged in spaced relation, with which the ends of the assembly are engagcable, and between which the assembly of laminas is peripherally exposed, said heads being recessed to receive molten metal and to mold the metal into terminal rings contiguous to the ends of the assembly and integral bars extending through the passages connecting the rings one with another.

9. The herein described process of producing squirrel cage rotors :for electric motors, including asseinblying a plurality of Aperforated laminaA into a compact body with the perforations disposed to form continuous passages therethrough providing vent openings from said passages to the periphery of the body from said passages 'to atmosphere, positioning the ends of said body in mold forms with the periphery of the laminated body exposed, and casting molten metal within said mold forms to form terminal rings integrally interconnected.

l0. The herein described process of producing squirrel cage rotors for electric motors, including assemblying a plurality of perforated lamina: into a compact body with the perforations disposed in non-intersecting relation with the periphery of the assembly to i'orm continuous passages therethrough providing spaced vent openings in the periphery of the assembly communicating with the passages, positioning contractible core bodies at the ends of the rotor body, casting molten metal about the core bodies and through the passages.

ll. A device for molding conductors in an assembly of perforated laminas, the perforations of which are relatively disposed to afford continuous passages through the assembly, comprising in combination a pair of permanently molding heads arranged in spaced relation, said heads being split so as to open in a plane parallel to the plane of said laminae, the ends of said assembly engaging said permanent molding heads between which the assembly of the laminae is peripherally exposed, and concentric yielding core rings within said mold forms contiguous to the ends of the body, said mold heads, said cores and said body forming a channel to receive the molten metal and to mold the metal into terminal rings contiguous with the ends of assembly and integral bars extending through the passages connecting the rings one with another.

l2. A device for molding conductors carried by an assembly of perforated lamin, the perforations of which are relatively disposed to a1.'- ford continuous passages through the assembly comprising in combination a pair of permanently split molding heads arranged in spaced relation, each of said heads having a cylindrical recess for receiving the assembly, and cylindrical sand cores disposed in said recesses and concentric therewith to hold the assembly in spaced relation with respect to the ends of said cylindrical recesses; said recesses, said cores, and said assembly cooperating to form channels for receiving molten metal and for molding the metal into terminal rings contiguous to the ends of the assembly and bars spaced at intervals extending through the passages connecting the rings one with another. 13. A device for molding conductors associated with an assembly of perforated lamin the perforations of which are relatively disposed to afford continuous passages through the assembly comprising in combination a pair of permanently split molding heads arranged in spaced relation, said heads being pivotally mounted so as to open along the split to receive an assembly of lamin, said heads when closed having a cylindrical recess, removable cores mounted in said recesses. so as toco-operate with the assembly and outer walls of the recesses to form closed channels for receiving molten metal and for molding the metal into terminal rings contiguous to the ends of the assembly and bars spaced at intervals extending through the passages connecting the rings one with another.

14. A device for molding the terminal rings contiguous with the ends of a laminated armature assembly and conductors spaced at intervals extending through passages in the armature, comprising in combination a pair ofv molding heads arranged in spaced relation, said heads being split so as to open radially with respect to the axis of said armature, the periphery of said laminations engaging said permanent molding heads between which the periphery of the armature assembly is exposed, and concentric yielding core rings within said heads contiguous to the ends of the armature, said mold heads, said core rings, and said armature forming a channel for receiving the molten metal and for molding the metal into terminal rings contiguous with the armature and conductors extending through the passages connecting the rings one with another. y

15. A device for molding an armature assembly having perforated lamin, Asaid perforations being relatively disposed to afford continuous passages through the assembly, comprising in combination a pair ot permanent molding heads arranged in spaced relation, each of said heads being split and having a cylindrical recessl for receiving the armature assembly and cylindrical sand cores disposed in said recesses and concentric therewith to hold the amature in -spaced relation with respect to the ends of said cylindrical recesses; the walls of said recesses, said cores and said assembly cao-operating to form a channel for receiving molten metal and for molding the metal into terminal rings contiguous to the ends of the assembly and bars spaced at intervals extending through said passages connecting the rings one with another.

16. A device for molding the terminal rings contiguous to the ends of an armature assembly having perforated lamin, the periorations of which are relatively disposed and for molding conductors located in said passages for connecting the terminal rings one with another, comprising in combination, a pair of molding heads arranged in spaced relation, said molding heads being split so as to open and close in a direction radially with respect to the axis of the armature assembly, each of said heads when closed having cylindrical recesses for receiving the armature assembly and removable cores mounted in said recesses for spacing the armature assembly with respect to said heads and so as to co-operate with the armature assembly and the outer walls of said recesses to form closed channels for receiving the molten metal and for molding the metal into terminal rings contiguous to the ends of the assembly and' interval spaced bars extending through the passages connecting the rings one with another.

EvERETr RALARsH. 

